Today it is very common that quick couplers are used for connecting different tools to an earth moving machine, for example an excavator, backhoe loader or a digger. With the quick coupler the driver can quickly and simply switch between different tools, for example different buckets, which can be used for s certain work condition. The quick coupling is mounted directly on the excavator art or on a on the arm mounted tilt rotator which allow tool movement in all directions. It can also be integrated in the tilt rotator. The quick coupling has in its lower part a locking mechanism adapted to lock the tool, either mechanically or with a hydraulically controlled lock. The locking mechanism often comprises a solid grip and a locking wedge or locking pins which locks the tool around parallel axles attached to the attachment bracket.
Quick couplers can be divided into two groups; universal or dedicated. Universal quick couplers are characterized in that the quick coupler is constructed to be able to be used on tools originating from different tool manufactures. Since the tools originate from different tool manufacturers or different excavator models, the distance between the parallel axles can vary and the diameter of the axles can be different. Thus, a universal quick coupler normally fits tools with different distances between the axles and sometimes also fit tools with different axle diameter. Dedicated quick couplers are, on the other hand, based on a standard, which result in that the quick coupler only fits if the tool follows the standard from which the quick coupler is constructed. Only the upper part, i.e. the part mounted adjacent the excavator arm, varies while the locking mechanism follows a standard. The most common standard for quick couplers on the Nordic market is symmetrical quick couplers, which are based on a gate with two parallel axles.
A problem with quick couplers of today is that it is a large risk that the driver drops the tool during the connection of the tool to the excavator, since the driver believe that the tool is securely locked with the locking mechanism even though this is not the case. The tool is lifted and run the risk of falling out from the front grip of the tool coupler due to gliding of the tool front axle.
A number of attempts have been made to solve the above mentioned problem. In patent application US2008/0193210A1 it is disclosed a coupling arrangement between a boom and a tool comprising a safety mechanism to prevent unintentional release of the tool. The document discloses a rotatable safety locking part which is spring suspended and biased towards a locking position. The locking part is with lock lever arms connected to a hydraulic cylinder part. The disadvantage with this solution is that it is not possible to securely lock the arrangement in all positions of the locking arrangement. For example when the hydraulic cylinder is in a locking position for safety locking, the safety locking part cannot rotate to receive an attachment pin. The positioning of an attachment pin first requires an activation of the hydraulic cylinder.
WO2008/051095 A2 discloses a safety lock for one of the attachment pins comprising an hydraulic cylinder. Unlocking and locking of the safety lock occur actively through the cylinder. Just as in the previous mentioned document this solution does not permit locking of the safety lock for a locked position of the locking arrangement.
EP1318242 B1 discloses a system for making safety locking possible. The disadvantage with the system is that safety locking is not possible when the locking arrangement is in a locked position. The positioning of the attachment pin in a cut out is not possible when the locking arrangement is locked, only when it is open.
WO2010/062193A1 discloses a coupling arrangement for attachment of a working tool and a method for unlocking which requires several steps. The snap locking of a first attachment pin is possible by a floatingly suspended hydraulic cylinder, i.e. arranged to be able to move up and down in the coupling arrangement. The disengagement of the safety lock occurs actively by contraction of the hydraulic cylinder which thus is connected for this purpose. The disadvantage with this solution is that the floating suspension of a hydraulic cylinder, i.e. by letting a large number of included components be moveable, increases the risk of fatigue of the parts over time and thereto also the risk of failure in the locking arrangement which is a safety risk. In a manufacturing perspective it is also a disadvantage to be forced to predefine an exact movement space for the hydraulic cylinder to make unlocking possible.
WO2005/026454 A1 discloses a safety lock for quick coupling of a tool. Safety locking is however not possible when the locking arrangement is in a locked position, and it requires a 180° rotation for unlocking.
Another problem with quick couplers of today is that the lock indication often is indistinct and not always secure. Today normally an indicator rod/indicator pin is used which is connected to the locking arrangement of the quick coupler. This means that when the locking arrangement is retracted into the holder the lock is opened and the indicator rod becomes visible, which indicates that the lock is open. Such solutions are for example disclosed in WO02097201A1, U.S. Pat. No. 6,379,075B1 and U.S. Pat. No. 6,132,130A. Thus, the normal is that the quick coupler has a negative lock indication, i.e. it indicates when the lock is open. The risk with this solution is, if the indicator rod in either way is broken or removed the driver may believe that the lock is closed, since no indicator rod is visible, while it actually is open. In such case the risk is large that the tool is dropped, which can be dangerous for personnel working in the vicinity of the excavator.
Other locking arrangements are also know which makes it possible to indicate when the lock is locked. Such quick coupler lock indication arrangements are for example shown in US20100189535A1, EP0527733B1 and U.S. Pat. No. 5,692,855A.
In both US20100189535A1 and EP0527733B1 a locking arrangement is disclosed having the shape of a, in relation to the quick coupler, laterally extending hydraulically actuated pin, which both see to that the lock remains locked and which, with a colored outer part visible for the driver, indicates that this is the case. U.S. Pat. No. 5,692,855A shows a coupling arrangement where a handle visible for the observer is turned together with the locking arrangement and indicates locked and unlocked position, respectively.
These solutions either demand an extra hydraulic actuator and/or several mechanically connected components which can be loose or break. Thus, there is a need for a simple and reliable lock indicator for a quick coupler which clearly indicated for that driver that the tool is securely locked to the excavator.